I would personally go with the 225dx. They are a very reliable machine, and has suspension. The suspension is the "get it" for me. It makes a much smoother ride with a shock in the rear. The suspension is by no means meant for jumping, but for trails it works great. I agree that the Honda models are easier to find parts for, and the motors are a little better built, but finding parts for the yamaha are not at all impossible, and maintanance isnt bad either. Many parts from other yamaha 200 models interchange as well. For what it is and cost, you should just about be able to pick up a Honda 200x for that price. That would have both choices beat, in suspension and power. Best trail bike ever. Good luck!
THE 80's RAGE! Currently owns:
81, 85 Yamaha Tri Moto 125
83 Yamaha Tri Moto 200 x2
82,83 Yamaha Tri Moto 175 project
85 Yamaha Tri Z 250
84 Kawasaki Tecate 250
84 Honda ATC 70
85 Honda ATC 350X
84 Honda ATC 250R
(2) 84 Honda ATC 200x
82, 83 Honda ATC 185s
81 ATC 200
Lots of other parts and bikes